1. Field of the Invention
The present invention relates to a power supplying apparatus and a display apparatus including the same.
2. Discussion of the Related Art
Generally, a power supplying apparatus rectifies an alternating current voltage and converts the alternating current voltage to a direct current voltage, or provides a direct current voltage required for various apparatuses (for example, display device and light emitting diode) by boosting or decompressing an alternating current voltage to a direct current voltage.
FIG. 1 is a diagram illustrating a power supplying apparatus of the related art.
Referring to FIG. 1, the power supplying apparatus of the related art includes a direct current-to-direct current converter 10, an under voltage detector 20, and a switching controller 30.
The direct current-to-direct current converter 10 converts an input power Vin to a direct current voltage and outputs the converted voltage. The direct current-to-direct current converter 10 includes an inductor L, a diode D, a switching element Psw, and a capacitor C. The direct current-to-direct current converter 10 converts the input power Vin to the direct current voltage in accordance with switching of the switching element Psw based on a pulse width modulation signal SPWM supplied from the switching controller 30. In other words, if the switching element Psw is turned on, a current flows to the inductor L by means of the input power Vin, whereby energy is accumulated in the inductor L. If the switching element Psw is turned off, the energy accumulated in the inductor L is added to the input power Vin, is rectified by the diode D, and is planarized by the capacitor C, whereby the energy is output as an output voltage Vout.
The under voltage detector 20, as shown in FIG. 2, generates an under voltage lock out signal UVLO of a high state and supplies the generated under voltage lock out signal to the switching controller 30 only if the voltage of the input power Vin is less than a reference under voltage detection voltage Vref_UVLO, thereby preventing a circuit, to which the input power Vin is supplied, from being operated in error.
The switching controller 30 generates a pulse width modulation signal SPWM by receiving the output voltage Vout fed back from the direct current-to-direct current converter 10, and uniformly controls the output voltage Vout of the direct current-to-direct current converter 10 by using the pulse width modulation signal SPWM only if the under voltage lock out UVLO signal of low state is supplied from the under voltage detector 20.
Meanwhile, according to the power supplying apparatus of the related art, if load is increased instantaneously and instantaneous voltage dip of the input power Vin occurs during inrush current, the under voltage lock out UVLO signal of high state is generated by the under voltage detector 20, whereby the under voltage lock out function may be performed. In order to prevent the circuit, to which the input power Vin is supplied, from being operated in error, during abnormal voltage dip of the input power Vin, the under voltage lock out function should be performed. However, in the display apparatus, etc., it may be preferable for stable operation that instantaneous voltage dip of the input power Vin is disregarded.
In this respect, in the power supplying apparatus applied to the display apparatus, the reference under voltage detection voltage Vref_UVLO is lowered so that the under voltage lock out function may not be performed during instantaneous voltage dip of the input power Vin, whereby the voltage range of the input power Vin is increased.
However, if the reference under voltage detection voltage Vref_UVLO for the under voltage lock out function is lowered to increase the voltage range of the input power Vin, the input current needs to be increased as the input power Vin is lowered. For this reason, as shown in FIG. 3, since the input current of each of the switching element Psw, the inductor L and the diode D is increased in accordance with the change of the input power Vin, a problem occurs in that a chip size of the integrated circuit IC is increased and current rating of each of the switching element Psw, the inductor L and the diode D should be enhanced. In order to solve this problem, if the reference under voltage detection voltage Vref_UVLO for the under voltage lock out function is increased, the under voltage lock out function is performed even in case of instantaneous voltage dip.
Accordingly, it is required that the under voltage lock out function should not be performed for instantaneous voltage dip even in case that the reference under voltage detection voltage Vref_UVLO is set at high level.